If you are bound for New York City, be sure to stop by Grand Central Terminal to explore its well-known (and not so well-known) idiosyncrasies.

Manhattan’s second most visited tourist site was built in 1913 as a result of one of the city's most tragic train accidents. Envisioned by the self-taught engineer William Wilgus, the terminal is a civic engineering masterpiece that required no public funding. Thanks to Wilgus’ use of new electric trains, tracks could be built deep enough underground to make use of the “air space” above to lease to developers and merchants. And just like everything else in New York, it couldn’t just be grand, it had to be beautiful.

The terminal's main concourse is an exceptional Beaux Arts building that welcomes over 750,000 people. Grand Central Terminal is not only the world’s largest train terminal, it is also living history with 101 years of hidden passageways and secrets to share with curious visitors. Here are 11 of our favorites.